Techniques for acquiring medical image data, rendering 3D models of an object from such data and allowing an operator to view the virtual object are well known. For example, U.S. Pat. No. 6,343,936 to Kaufman et al. entitled “System and Method for Performing a Three Dimensional Virtual Examination, Navigation and Visualization” discloses such systems and methods. Virtual colonoscopy is an important application for such systems. The ability to have the colon interior examined using a non-invasive medical imaging method as opposed to conventional invasive techniques will make the procedure more widely used and will lead to early detection of cancerous polyps in a larger number of cases. In this regard, the '936 patent discloses a method of detecting polyps within a colon lumen. The disclosure in the '936 patent presents an initial method for effectively detecting polyps. It is expected that improvements in such techniques are desirable to further improve the results of automatic polyp detection.